1) Field of the Invention
The present invention relates to a positioning controller for positioning a movable member such as a gear ratio determining member which determines a gear ratio of an automatic transmission mounted on an automobile or the like.
2) Description of the Related Art
In an apparatus used for positioning a movable member, such as a positioning table of a machine tool for a work piece, the movable member such as a nut in mesh with an elongated bolt is generally actuated by transmitting a turning force generated by a motor to the bolt through a gear attached thereto, thereby allowing the nut to travel along an axial direction of the bolt.
A positioning control or a coordinate control of the nut toward the target position can be performed, for example, by way of a feedback control which controls the required number of rotations of the motor by detecting a present position of the nut from an output signal of an encoder provided on a driving source, i.e., the motor.
Alternatively, the control can be performed by way of a feedback control which controls the required number of rotations of the motor by detecting the position of the nut from the angle of a member such as a sloped board which is mechanically linked to the movable nut, and such angle is detected by an angle sensor.
Those conventional control methods require a detecting sensor, in addition to a control unit such as a computer, to detect the present position of the nut in order to determine the difference between the present position and the target position of the nut, or set point, which results in an increase in overall system cost.